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Coffee Cart : Sonic Agitator Concept

"Coffee Cart: Our mission to reimagine the office coffee cart" is an on-going collaboration between Koss and Stone Creek Coffee. So far we've covered our initial brainstorm and visit to Stone Creek. Today, we join coffee and sound with the Sonic Agitator. See our initial sketches and proof of concept model below.

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SHAKE IT UP: During our initial brainstorm, Nick from Koss had the idea to create 'sonic coasters.' The coasters were a way of merging coffee with sound. A mug would sit on top of small speaker playing music, and the surface of the coffee would shake along to the beat.

The idea resurfaced later at our meeting with Stone Creek.  Joel gave a brief explanation of the brewing process. He noted that once the brewed coffee is in the carafe, it needs to be stirred. Nick suggested that instead of stirring, we employ the principles of cymatics and use sound waves to mix the brew. We shifted the concept from coasters to a Sonic Agitator.

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GUTS: Upon returning to the office, we looked around for materials to build a proof of concept model. We found: a discarded subwoofer, 9v battery clips, small amp, and some plywood. The subwoofer speaker is relatively small, only about 4" diameter. The power from the amp was pretty low too, but for a proof of concept it would be good enough.

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CUT: We used the subwoofer's dimensions for the model's base. The upper shelf mirrors the base, allowing room for a single mug. Our office shares a parking lot with a building supply store, so we ran over and picked up a sheet of clear polycarbonate. The sheet would be perforated using a hand drill, and fixed to spacers just above the speaker. We chose polycarbonate so we could see the speaker's diaphragm vibrate. We gathered up a sheet of 1/2"  plywood, measured out our cuts, and hit the table saw.

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WHAT YOU ARE ABOUT TO HEAR IS A TEST: The fully assembled proof of concept model.

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QUICKNESS IS KEY: The clearance for the volume knob and input were very small, and the components were all mounted directly to the amplifier board. Attaching the board to the plywood was possible, but would have required a fair amount of precision, accuracy, and time. For the sake of speed, we improvised by cutting a hole in the plywood and mounted the board to this plastic key card.

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SHAKEN, NOT STIRRED: We enclosed the top chamber on all but one side. The initial plan also called for this section to be lightly soundproofed. However, we opted to test before experimenting with sound insulation.

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SYNTHESIS: Our analog modeling digital synth was used to generate the tone. We shifted the octave all the way down, maxed the volume, and played a note. The speaker let out a belch like a foghorn and the agitator started rattling on the tabletop. We brewed some coffee and placed a single mug on the perf sheet.

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SUCCESS: At the highest volume, the coffee's surface rippled in sync with the sound from the speaker. After a closer look, we noticed the perf screen bowed under the weight of the mug. The diaphragm and screen made contact, in essence the two were mechanically coupled. We figure this contributed to much of the rippling. The effect was very minor, but for our low powered proof of concept it demonstrated viability.

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BOTTOMS UP: A quick look at the bottom of the unit reveals many of its shortcomings. First is the weak power supply. We rigged up a 9v battery which provided decent power, but ideally we'd like more. Additionally, the speaker was ported. According to our engineers, as the diaphragm and screen were mechanically coupled, we were likely to get a better result if the speaker did not have a port. These are all things we are considering further for our full scale version.

Next step: finalize the cart design... check back for more updates!


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